The present invention relates to an inverse Cassegrain antenna for use in look-out or tracking and which is able to supply a widened beam either in the ground visualization elevation plane or in the bearing plane (anti-collision), whilst still retaining the qualities of a fine primary beam.
In a multiple function radar, it is desirable for the beam transmitted by the antenna to have, at a given moment, a shape adapted to the function for which it is to be used. On simple antennas, this has already been carried out by switching the primary sources or by modifying the shape of the antenna. However, this method of adapting an antenna to different functions of a radar does not give good results in the case of an inverse Cassegrain antenna. The performance of the Cassegrain antenna is reduced if the primary sources thereof are multiplied or if the parabolic deflector is deformed, making it necessary to modify the beam focusing device.
An advantageous way in which an inverse Cassegrain antenna with multiple functions can be realized is to modify the shape of the polarization rotation mirror with which it is equipped.